I'd say make sure you eyeball any device before you buy. Definitely make sure the resolution has at least 720+ (usually comes in either 480, 768, 1024 or 1080) lines otherwise you might as well stick with what you've got. And check the warranty's. I know Samsung and Sony are considered the leaders in the market.Also check what inputs it has HDMI is nice to have.
1. Compare apples with apples, HDTV comes in a few flavours 720p, 1080i & 1080p, also compare native pixel resolutions
2. There is a good chance you will want to connect HD equip to it in the future so if possible it should have an HDMI interface with HDCP (to watch copy protected retail content)